1. Field of the Invention
The present invention relates to a semiconductor device including an oxide semiconductor and a manufacturing method of the semiconductor device.
In this specification, a semiconductor device means a device which can function by utilizing semiconductor characteristics, and an electrooptic device, a semiconductor circuit, and an electronic device are all semiconductor devices.
2. Description of the Related Art
In recent years, semiconductor devices have been developed to be used mainly for an LSI, a CPU, or a memory. A CPU is an aggregation of semiconductor elements each provided with an electrode which is a connection terminal, which includes a semiconductor integrated circuit (including at least a transistor and a memory) separated from a semiconductor wafer.
A semiconductor circuit (IC chip) of an LSI, a CPU, or a memory is mounted on a circuit board, for example, a printed wiring board, to be used as one of components of a variety of electronic devices.
A technique for manufacturing a transistor by using an oxide semiconductor film for a channel formation region, or the like has been attracting attention. Examples of such a transistor include a transistor in which zinc oxide (ZnO) is used as an oxide semiconductor film and a transistor in which InGaO3(ZnO)m is used as an oxide semiconductor film. A technique in which a switching element, such as a transistor, in which a channel formation region is formed in an oxide semiconductor film is used for manufacturing an active matrix display device has also been developed.
Patent Document 1 discloses a three-layer structure in which a first multi-component oxide semiconductor layer is provided over a substrate, a one-component oxide semiconductor layer is stacked over the first multi-component oxide semiconductor layer, and a second multi-component oxide semiconductor layer is stacked over the one-component oxide semiconductor layer.
Non-Patent Document 1 discloses a transistor having a stack of oxide semiconductors.